The Eustachian tube (ET) is a very narrow air passage in the wall of a human's middle ear which connects it to the nasopharynx, a midline air filled space in the back of the nose. The tube is approximately 37 mm long and is slightly hourglass shaped, flattened anterior-posteriorly. The small lumen of the Eustachian tube permits the exchange of ambient gases between the middle ear and nasopharynx and the transport of middle ear secretions into the nasopharynx. The lateral one-third of the Eustachian tube (tympanic segment) is made of bone, while the medial two-thirds (pharyngeal segment) is cartilaginous. A constriction at the junction of the bony and cartilaginous segments, called the isthmus, may be as narrow as 1.0 mm by 1.5 mm. This tube regulates the intermittent exchange of air to or from the middle ear space to maintain equal pressure on both sides of the eardrum. The surface of the epithelium of the middle ear and Eustachian tube is covered by a raucous blanket, which is a defensive barrier against inhaled pollutants and a multitude of microorganisms. Middle ear secretions are normally eliminated through the ET.
In humans, the Eustachian tube is a very unique structure that enables the middle ear pressure to adapt to various altitude changes and, when closed, it prevents the endogenous intraoral sounds of respiration and vocalization from reaching the middle ear to compete with and mask out the environmental sounds for reception and relay to the inner ear.
Normally, the Eustachian tube maintains an isobaric relationship between the middle ear space and the ambient air exchanged within the nasal passages during breathing. The critical opening pressure for the tube to ventilate the middle ear chamber is related to the surface tension and diameter of the ET opening onto the lateral wall of the nasopharynx. This is modified by the rheological properties of the mucus blanket on the endothelial tissues. In its natural state, the Eustachian tube orifice is always closed, but may actively open spontaneously several times a minute or when swallowing or yawning. As integral part of the middle ear, the Eustachian tube functions to prevent and ameliorate the same inflammatory diseases such as otitis media etc. and its complications.
Blockage of the Eustachian tube isolates the middle ear space from the outside environment. The lining of the middle ear absorbs the trapped air and creates a negative pressure that pulls the eardrum inward. The eardrum is thin and pliable, like plastic wrap, and is densely innervated. When it becomes stretched inward, patients often experience pain, pressure, and hearing loss. Long-term blockage of the Eustachian tube leads to the accumulation of fluid in the middle ear space that further increases the pressure and hearing loss. This is called serous otitis media. Should bacteria contaminate this fluid, a middle ear infection may result, called acute otitis media.
Failure of the Eustachian tube to open during yawning, swallowing or barometric pressure changes between the middle ear and pharynx is called Eustachian tube dysfunction. This can occur when the lining of the nose becomes irritated and inflamed, narrowing the Eustachian tube opening or its passageway. Illnesses like the common cold or influenza are often to blame. Pollution and cigarette smoke can also cause Eustachian tube dysfunction. In many areas of the country, nasal allergy (allergic rhinitis) is the major cause of Eustachian tube dysfunction. For reasons that are unclear, the incidence of allergies is increasing in the United States. Obesity can also predispose a patient to Eustachian tube dysfunction because of excess fatty deposits around the passageway of the Eustachian tube. Rarely, Eustachian tube blockage may be the sign of a more serious problem such as nasal polyps, a cleft palate, or a skull base tumor.
Young children (especially ages 1 to 6 years) are at particular risk for Eustachian tube dysfunction, serous otitis media, and acute otitis media because they have very narrow Eustachian tubes. Also, they may have adenoid enlargement that can block the opening of the Eustachian tube. Since children in daycare are highly prone to getting upper respiratory tract infections, they tend to get more ear infections compared to children that are cared for at home.
The anatomy of the Eustachian tube in infants and young children is different than in adults. It runs horizontally, rather than sloping downward from the middle ear. The horizontal course of the Eustachian tube also permits easy transfer of bacteria from the nose to the middle ear space. This is another reason that children are so prone to middle ear infections.
Certain bacteria are reported to be the primary causes of acute otitis media (AOM) and are detected in about 60% of cases. The bacteria most commonly causing ear infections are: Streptococcus pneumoniae (also called S. pneumoniae or pneumococcus), the most common bacterial cause of acute otitis media, causing about 40% to 80% of cases in the U.S.; Haemophilus influenzae, the next most common culprit and is responsible for 20% to 30% of acute infections; and Moraxella catarrhalis, also a common infectious agent, responsible for 10% to 20% of acute infections. Less common bacteria are Streptococcus pyogenes and Staphylococcus aureus. 
A serious sequalae of bacterial chronic otitis media includes otitis media with effusion (OME) that is associated with complications such as a ruptured tympanic membrane (TM). The failure of the Eustachian tube to expel or eliminate the natural secretions, microorganisms, biofilms and toxic products result in destruction of the tissues, TM rupture and hearing loss. When the fluid becomes infected the increased pressure is very painful and causes the delicate tympanic membrane to rupture releasing the toxins into the external ear canal for elimination
In the past, antibiotics have been the mainstay of eliminating bacterial microorganisms by direct biochemical interaction. However, antibiotics can only treat the infection when and if the agent is capable of penetrating the biofilm barrier and altering the biochemistry of the microorganism internally.
Of note, about 15% of these bacteria are now believed to be resistant to the first-choice antibiotics. With the overuse of antibiotics and the development of resistance by microorganisms, such treatment has become less effective and frequent side effects have become common.
More recently, because the chemical structure of the newer anti-infective agents are more complex, antibiotics are not absorbable in the gastrointestinal tract, necessitating that the medication be administered by intravenous injection which is further associated with serious side effects such as ototoxicity, hearing loss and tinnitus, and allergic reactions. Scientific studies have identified prenatal markers, such as smoking, that predispose the infant to develop middle ear infections.
Various medical treatments other than antibiotics are utilized to alleviate the symptoms of ETD. In many cases, leaving it alone without any specific treatment is sufficient as the condition may only be temporary as the result of a cold or other respiratory disease. Swallowing and chewing are encouraged to manipulate the tissues surrounding the Eustachian tube thereby promoting the opening of the tube to equalize pressure to the middle ear. Self-inflation can be accomplished by doing a gentle Valsalva maneuver to force air up into the Eustachian tube. However, blowing too forcibly can make the condition worse by forcing fluids and bacteria from the throat into the tube. These procedures may not be sufficient to provide the individual with the length and degree of relief desired.
Synthetic and natural (pork or beef lung) pulmonary surfactant compounds have been in use in neonatology since the early 1980's. Tracheal administration of surfactant to premature infants with respiratory distress syndrome improves lung compliance, opens small air passages and has significantly improved life expectancy. Studies in the 1960's were unsuccessful because isolated surfactant proteins alone were being used. It was not until the addition of the emulsifier/spreading agent phosphatidylglycerol, derived from egg lecithin, that efficacy was finally demonstrated. Emulsifiers not only distribute pulmonary surfactant but also change its physical properties to be more fluid.
In animal studies, bacteria are injected into the middle ear space to increase Eustachian tube opening pressure. Nebulized bovine pulmonary surfactant compound administered intranasally to these animals demonstrated improved clearance of fluid from the middle ear, thus decreasing Eustachian tube opening pressure. However, individuals with allergies to beef or pork protein may suffer complications from this natural surfactant therapy, and the method of nebulized administration may be cost prohibitive for widespread use.
Medical professionals can also recommend or prescribe a variety of drugs to treat ETD. Decongestants, either orally or nasally, may promote the opening of the Eustachian tube. Nasal corticosteroids can relieve tissue inflammation, one of the major causes of ETD. Antihistamines may reduce the amount of rhinorrhea and post-nasal drainage that may contribute to ETD. Use of over-the-counter or prescription drugs, which are absorbed into the user's system, may not be tolerated by the individual because of various side effects.
It is therefore desirable to provide a composition for the treatment of Eustachian tube dysfunction that is effective in unblocking a clogged Eustachian tube and that is well tolerated without undesirable side effects.